A High-resolution Active Fiber Bragg Grating Multiplexing Sensor Systems

The thesis makes some studies for the applications of fiber Bragg grating sensor network:1. Based on an amplified spontaneous emission (ASE) source, a ring-cavity fiber laser, in which sensor element acted as the reflector of the cavity, was achieved with high-signal noise ratio (SNR) and high-power. It was demonstrated that the output power was maximum, when output coupler ratio of the coupler was seventy percent.2. Based on interoferometric technique, a parasitic interference configuration was introduced to transpose the wavelength-shift signal into phase-shift signal; the strains were demodulated by measuring the phase change of the signal with a phase-meter. The sensing sensitivity of this system , which is with a resolution of 6.2 nε, was demonstrated to be1.53 /uε, experimentally ,It basically matches the prospected value of1.61/uε.3. Passive and active time-domain demodulation schemes were demonstrated based on a fiber Bragg grating used as a tunable filter controlled by a piezoelectric stack, which was driven by an electrical sine wave signal .The measured strain applied on the sensor axially could be judged by observing the interval of the output between notches within a driving period in time-domain.4. A 8-cascaded wavelength-division-multiplexed fiber Bragg gratingsensor system was interrogated by changing voltage acting on a employed tunable Fabry-Perot filter, and a feedback loop was introduced to make filter track the shifted wavelength of the sensor. At the same time an unbalanced scanning Michelson interferometer was introduced to demodulate sensor signal. The sensing sensitivity of this system, wasdemonstrated to be 0.56 / uε, experimentally. It basically matches the prospected value of 0.57/uε...